A traditional process control system receives alarms from external equipment, such as sensors, PLC's, and controllers supervising and controlling the process. The process control system comprises an alarm system including an alarm server that puts together the alarms and produces alarm lists for the operator(s). An alarm list contains active alarms and non-active alarms that have not been acknowledged by the operator. An alarm is active e.g. if an upper limit is exceeded and becomes inactive when it is below the upper limit. The alarm lists are displayed on a human machine interface of the process control system in real time so that the operator immediately is informed about a new alarm. In a large control system, different operators can be responsible for different parts of the process, for example, an operator may be responsible for different process sections of a factory and is only interested in statistics for its own sections. Therefore it is common that the received alarms are sorted into different alarm lists and each operator can view its own alarm list including alarms from the parts of the process, which the operator is responsible for.
By sorting the alarms into different alarm lists, the number of alarms presented to a certain operator is reduced. In spite of this measure, the number of alarms presented to the operator can be extremely large and accordingly it can be difficult for the operator(s) to evaluate and act to resolve all the alarms. The number of alarms can be unreasonably high if the engineering project has not selected alarm limits carefully but rather used default limits for most actors. A known solution to this problem is to use an external alarm management system that analyzes the alarms, provides statistics on the alarms, and generates reports and trends based on the received alarms. The alarm management system calculates a plurality of key performance indicators, KPI, based on the alarms received from the control system. Example of statistics provided by the alarm management system is the ten most common alarms, the ten longest standing alarms, the number of alarms over time, and alarm priority distribution.
The alarm management system comprises a database for storing the received alarms and software for analyzing and performing statistics on the alarms stored in the database. The software and database are hosted on an external computer.
All alarms received by the process control system are transmitted to the external database that resides outside the process control system. Queries are then performed to the database, which results in reports in the form of text and diagrams. Analyzing of the alarms and calculation of the statistic is typically initiated manually of a system engineer, who demands that a certain type of statistics is provided.
The purpose of the alarm management system is to reduce the number of irrelevant alarms and make it possible to select the most important alarms among the huge amount of alarms generated. A problem with today's alarm management systems is that they add additional complexity and costs to the process control system. The external database has to be installed together with the control system, which is time consuming and adds complexity. The database is often provided by a third party vendor, which adds licensing costs. Reports generated from the database do not handle real time data, since the database reports give a snapshot of the data. Further, it is not possible to have a trend with real time updates displayed. It is also hard to know which of the alarms transmitted to database that was really presented to a particular operator.